1. Field of the Invention
This invention relates to a spectroscopic optical system, for example a system for Raman spectroscopy to measure a blood and/or tissue analyte such as glucose, cholesterol, collagen, β-Hydroxybutyrate or keratin.
2. Description of the Related Art
Blood analytes are typically measured by drawing a small amount of blood from a person and then analyzing that blood using any of numerous known techniques. For example, people suffering from diabetes usually draw a drop of blood several times a day in order to measure their glucose levels using a handheld glucose measuring device.
Because blood must be drawn, these typical techniques are invasive and inconvenient. As a result, only a limited number of samples typically are taken per day outside of hospitals and medical care facilities where blood can be drawn frequently or continuously.
Use of spectroscopy to measure blood and/or tissue analytes non-invasively has been proposed. In particular, Raman spectroscopy has been proposed as a technology that could permit frequent or even constant non-invasive measuring of blood analytes. U.S. Pat. No. 7,039,448, titled “Zero Corrected Optical Blood Analyte Detector,” assigned to DIRAmed, LLC, discloses one technique for using a stable, naturally occurring tissue component such as cholesterol to calibrate a spectroscopic device for measuring a blood analyte. U.S. Pat. No. 7,039,448 is hereby incorporated by reference as if fully set forth herein.
Although techniques for measuring blood glucose in vivo using spectroscopy have been proposed, actual real-world implementation has proven to be very elusive. A book has even been written on the subject: The Pursuit of Noninvasive Glucose: “Hunting the Deceitful Turkey” by John L. Smith (copyright 2006).